1. Field of the Invention
This invention relates to the field of universal synchronous-asynchronous receiver/transmitters.
2. Background Art
Computers or other processing units are often coupled to peripheral devices such as printers, communication devices, etc. A communication program executed on the host computer controls the transfer of data from the host computer to the communications device. The central processing unit (CPU) or processor of the host computer implements the transmission of the data from memory to the communications device. A processor generally receives and transmits data in parallel. However, peripheral devices generally require serial data streams. When a communication device is coupled to a computer processor, the parallel output of the computer processor is first converted to serial output and provided through a serial port to the peripheral device. The peripheral device then operates on the serial data stream. For example, if the peripheral device is a modem, the serial data stream is modulated and transmitted on a transmission line.
Many communication devices such as modems or protocol converters are "intelligent," that is, they have their own processing means built in. When such an intelligent device receives a serial data stream, it converts the serial data stream to a parallel data stream for processing. Therefore, when a computer communicates with a peripheral device through a serial port, the data stream undergoes a parallel to serial to parallel conversion. The prior art methods of this parallel to serial to parallel conversion require dedicated hardware and software. In addition, special effort is required to perform format identification (data rate, parity, etc.). Known patterns are required and formats are often limited. This conversion also limits the maximum data rate.
In addition, the communication may be either asynchronous or synchronous. Many computer systems use one converting device for performing parallel to serial conversion on synchronous data and a separate converting device for asynchronous data. This is because there are standard interfaces for each type of communication. This results in complex circuitry requirements.
The transfer of the data from within the computer to the serial output also requires special formatting. This formatting control may come from customized software in the computer, or as either a software driver or separate processor communicating with a standardized software interface. The prior art provides solutions for only one of the above techniques at a time. This requires separate and distinct solutions which cannot be easily interchanged.
Therefore, it is an object of the present invention to provide a universal and configurable architecture for serial communications.
It is another object of the present invention to emulate the register set of a plurality of communication devices into a single device.
It is still another object of the present invention to provide a method and apparatus for converting parallel data and to implement protocol conversion on such data.